
package com.yesep.learn.jwt.util;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Scanner;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;

import cn.hutool.core.util.StrUtil;

/**
Google  Authenticator

 只从google出了双重身份验证后，就方便了大家，等同于有了google一个级别的安全，但是我们该怎么使用google authenticator (双重身份验证)，

下面是java的算法，这样大家都可以得到根据key得到公共的秘钥了,直接复制，记得导入JAR包：

commons-codec-1.8.jar

junit-4.10.jar

测试方法：

1、执行测试代码中的“genSecret”方法，将生成一个KEY（用户为testuser），URL打开是一张二维码图片。

2、在手机中下载“GOOGLE身份验证器”。

3、在身份验证器中配置账户，输入账户名（第一步中的用户testuser）、密钥（第一步生成的KEY），选择基于时间。

4、运行authcode方法将key和要测试的验证码带进去（codes，key），就可以知道是不是正确的秘钥了！返回值布尔

main我就不写了大家~~因为这个可以当做util工具直接调用就行了

* @Description:
*/
public class GoogleAuthenticator {

	// taken from Google pam docs - we probably don't need to mess with these
	public static final int SECRET_SIZE = 10;

	public static final String SEED = "g8GjEvTbW5oVSV7avLBdwIHqGlUYNzKFI7izOF8GwLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";

	public static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";

	int window_size = 3; // default 3 - max 17 (from google docs)最多可偏移的时间

	public void setWindowSize(int s) {
		if (s >= 1 && s <= 17)
			window_size = s;
	}

	public static Boolean authcode(String codes, String savedSecret) {
		// enter the code shown on device. Edit this and run it fast before the code expires!
		long code = Long.parseLong(codes);
		long t = System.currentTimeMillis();
		GoogleAuthenticator ga = new GoogleAuthenticator();
		ga.setWindowSize(15); // should give 5 * 30 seconds of grace...
		boolean r = ga.check_code(savedSecret, code, t);
		return r;
	}

	// 动态变化的密钥
	public static String generateSecretKey() {
		SecureRandom sr = null;
		try {
			sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);
			sr.setSeed(Base64.decodeBase64(SEED));
			byte[] buffer = sr.generateSeed(SECRET_SIZE);
			Base32 codec = new Base32();
			byte[] bEncodedKey = codec.encode(buffer);
			String encodedKey = new String(bEncodedKey);
			return encodedKey;
		} catch (NoSuchAlgorithmException e) {
			// should never occur... configuration error
		}
		return null;
	}

	public static String getQRBarcodeURL(String user, String host, String secret) {
		String format = "https://www.google.com/chart?chs=200x200&chld=M%%7C0&cht=qr&chl=otpauth://totp/%s@%s%%3Fsecret%%3D%s";
		return String.format(format, user, host, secret);
	}

	public boolean check_code(String secret, long code, long timeMsec) {
		Base32 codec = new Base32();
		byte[] decodedKey = codec.decode(secret);
		// convert unix msec time into a 30 second "window" this is per the TOTP spec (see the RFC for details)
		long t = (timeMsec / 1000L) / 30L;
		// Window is used to check codes generated in the near past.  You can use this value to tune how far you're willing to go.
		for (int i = -window_size; i <= window_size; ++i) {
			long hash;
			try {
				hash = verify_code(decodedKey, t + i);
			} catch (Exception e) {
				// Yes, this is bad form - but
				// the exceptions thrown would be rare and a static configuration problem
				e.printStackTrace();
				throw new RuntimeException(e.getMessage());
				// return false;
			}
			if (hash == code) {
				return true;
			}
		}
		// The validation code is invalid.
		return false;
	}

	private static int verify_code(byte[] key, long t) throws NoSuchAlgorithmException, InvalidKeyException {
		byte[] data = new byte[8];
		long value = t;
		for (int i = 8; i-- > 0; value >>>= 8) {
			data[i] = (byte) value;
		}
		SecretKeySpec signKey = new SecretKeySpec(key, "HmacSHA1");
		Mac mac = Mac.getInstance("HmacSHA1");
		mac.init(signKey);
		byte[] hash = mac.doFinal(data);
		int offset = hash[20 - 1] & 0xF;
		// We're using a long because Java hasn't got unsigned int.
		long truncatedHash = 0;
		for (int i = 0; i < 4; ++i) {
			truncatedHash <<= 8;
			// We are dealing with signed bytes:
			// we just keep the first byte.
			truncatedHash |= (hash[offset + i] & 0xFF);
		}
		truncatedHash &= 0x7FFFFFFF;
		truncatedHash %= 1000000;
		return (int) truncatedHash;
	}

	public static void main(String[] args) throws Exception {
		String user = "guest", host = "yunjian-boot-admin";
		String secret = GoogleAuthenticator.generateSecretKey();
		System.out.println(secret);
		String url = GoogleAuthenticator.getQRBarcodeURL(user, host, secret);
		System.out.println(url);
		Scanner sc = new Scanner(System.in);
		while (true) {
			System.out.println("请输入动态密码：");
			String code = sc.nextLine();
			if (StrUtil.isBlank(code))
				break;
			boolean result = GoogleAuthenticator.authcode(code, secret);
			System.out.println(result);
		}
		sc.close();

	}
}
